Kids Research Express

Plant and animal species are dying out at an unprecedented rate (see Endangered Species ). Estimates range that from 4,000 to as many as 50,000 species per year become extinct. The leading cause of extinction is habitat destruction, particularly of the world’s richest ecosystems—tropical rain forests and coral reefs . If the world’s rain forests continue to be cut down at the current rate, they may completely disappear by the year 2030. In addition, if the world’s population continues to grow at its present rate and puts even more pressure on these habitats, they might well be destroyed sooner.

A significant portion of industry and transportation burns fossil fuels, such as gasoline . When these fuels burn, chemicals and particulate matter are released into the atmosphere. Although a vast number of substances contribute to air pollution , the most common air pollutants contain carbon , sulfur , and nitrogen . These chemicals interact with one another and with ultraviolet radiation in sunlight in dangerous ways. Smog , usually found in urban areas with large numbers of automobiles, forms when nitrogen oxides react with hydrocarbons in the air to produce aldehydes and ketones . Smog can cause serious health problems. Acid rain forms when sulfur dioxide and nitrous oxide transform into sulfuric acid and nitric acid in the atmosphere and come back to Earth in precipitation. Acid rain has made numerous lakes so acidic that they no longer support fish populations. Acid rain is also responsible for the decline of many forest ecosystems worldwide.

Estimates suggest that nearly 1.5 billion people worldwide lack safe drinking water and that at least 5 million deaths per year can be attributed to waterborne diseases. Water pollution may come from point sources or nonpoint sources. Point sources discharge pollutants from specific locations, such as factories, sewage treatment plants, and oil tankers. The technology exists to monitor and regulate point sources of pollution, although in some areas this occurs only sporadically. Pollution from nonpoint sources occurs when rainfall or snowmelt moves over and through the ground. As the runoff moves, it picks up and carries away pollutants, such as pesticides and fertilizers, depositing the pollutants into lakes, rivers, wetlands, coastal waters, and even underground sources of drinking water. Pollution arising from nonpoint sources accounts for a majority of the contaminants in streams and lakes. With almost 80 percent of the planet covered by oceans, people have long acted as if those

Water that collects beneath the ground is called groundwater . Worldwide, groundwater is 40 times more abundant than fresh water in streams and lakes. Although groundwater is a renewable resource, reserves replenish relatively slowly. Agricultural practices depending on this source of water need to change within a generation in order to save this groundwater source. In addition to groundwater depletion, scientists worry about groundwater contamination, which arises from leaking underground storage tanks, poorly designed industrial waste ponds, and seepage from the deep-well injection of hazardous wastes into underground geologic formations. By some estimates, on average, 25 percent of usable groundwater is contaminated, and in some areas as much as 75 percent is contaminated.

A number of toxic substances that humans encounter regularly may pose serious health risks. Pesticide residues on vegetable crops, mercury in fish, and many industrially produced chemicals may cause cancer, birth defects , genetic mutations, or death. Many chemicals have been found to mimic estrogen, the hormone that controls the development of the female reproductive system in a large number of animal species. Preliminary results indicate that these chemicals, in trace amounts, may disrupt development and lead to a host of serious problems in both males and females, including infertility , increased mortality of offspring, and behavioral changes such as increased aggression.

Studies have shown that not all individuals are equally exposed to pollution. For example, worldwide toxic-waste sites are more prevalent in poorer communities. Three of the five largest commercial hazardous-waste landfills in America are in predominantly black or Hispanic neighborhoods, and three out of every five black or Hispanic Americans live in the vicinity of an uncontrolled toxic-waste site. The wealth of a community is not nearly as good a predictor of hazardous-waste locations as the ethnic background of the residents, suggesting that the selection of sites for hazardous-waste disposal involves racism. Environmental racism takes international forms as well. American corporations often continue to produce dangerous, U.S.-banned chemicals and ship them to developing countries. Additionally, the developed world has shipped large amounts of toxic waste to developing countries for less-than-safe disposal. For instance, experts estimate that 50 to 80 percent of electronic waste pro

The limited supply of fossil fuels, coupled with their contributions to global warming, air pollution, and acid rain, makes it clear that alternative forms of energy will be needed to fuel industrial production and transportation. A number of energy alternatives are available, but many of these options are unlikely to replace fossil fuels in the foreseeable future because they cost more, produce less energy than fossil fuels, or pose safety risks. A handful of countries produce a portion of their electricity using nuclear energy . But many people oppose nuclear energy because an accident can cause massive devastation. The 1986 accident at the Chernobyl’ nuclear power plant in the Ukraine scattered radioactive contamination over a large part of Europe. Approximately 200,000 people were evacuated, and human health has been dramatically affected. Studies in 1999 found that the rate of thyroid cancer in young Ukrainian children was ten times higher than was the norm prior to the accident.